<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>清除默认样式</title>
  <style>
    * {
      padding: 0;
      margin: 0;
      box-sizing: border-box;
    }

    li {
      list-style: none;
    }
  </style>
</head>

<body>
  <h1>标题</h1>
  <p>pppp</p>
  <ul>
    <li>li</li>
  </ul>
</body>

</html>